Hi.

I use a folder named Private in my bookmarks and do a quick
attrib +h Private
to hide it and another quick
attrib -h Private
to unhide again. Actually they are both encapsulated in small batch files that change to the appropriate folder first, so that I can do the hide/unhide from anywhere on the shell. Also, I open a new shell window (excuse me: DOS window) for it and close it right after executing the script. That way, there is no visible trace of what I did.
You also need to make sure that there is no open Favorites view, or make sure they all get refreshed (and reflect the change). Otherwise, whoever sits at your desk could easily expand that favorites folder because it is still visible.

Of course, a more secure way would be to move that favorites folder named "Private" out of the main favorites folder so that it doesn't even exist anymore inside the favorites view.

Hope you could follow, and sorry for the late reply (well, sort of).

cu,
sven